Field of the Invention
The present invention relates to golf balls. Specifically, the present invention relates to improvement of dimples of golf balls.
Description of the Related Art
The greatest interest to golf players concerning golf balls is flight distance. Golf players place importance on flight distance particularly in a shot with a driver. There have been proposals for improvement of flight performance. JP2010-188199 discloses a golf ball that includes a core having a great surface hardness and a small central hardness.
Another interest to golf players concerning golf balls is feel at impact. Generally, players prefer soft feel at impact. Players place importance on feel at impact particularly in shots with a middle iron and with a short iron.
Golf balls have a large number of dimples on the surfaces thereof. The dimples disturb the air flow around the golf ball during flight to cause turbulent flow separation. This phenomenon is referred to as “turbulization”. Due to the turbulization, separation points of the air from the golf ball shift backwards leading to a reduction of drag. The turbulization promotes the displacement between the separation point on the upper side and the separation point on the lower side of the golf ball, which results from the backspin, thereby enhancing the lift force that acts upon the golf ball. Excellent dimples efficiently disturb the air flow. The excellent dimples produce a long flight distance.
There have been various proposals for dimples. JP2009-172192 (US2009/0191982) discloses a golf ball that has randomly arranged dimples. The dimple pattern of the golf ball is referred to as a random pattern. The random pattern can contribute to flight performance of the golf ball. JP2012-10822 (US2012/0004053) also discloses a golf ball having a random pattern.
JP2007-175267 (US2007/0149321) discloses a dimple pattern in which the number of units present in a high-latitude region is different from the number of units present in a low-latitude region. JP2007-195591 (US2007/0173354) discloses a dimple pattern in which the number of types of dimples present in a low-latitude region is greater than the number of types of dimples present in a high-latitude region. JP2013-153966 (US2013/0196791) discloses a dimple pattern in which the density of dimples is high and variations in sizes of dimples are small.
The greatest interest to golf players concerning golf balls is flight performance. Golf players desire golf balls having excellent flight performance. In light of flight performance, there is room for improvement in a dimple pattern.
Golf players also desire golf balls having excellent feel at impact.
Golf players also place importance on flight distance in a shot with an iron club as well as flight distance in a shot with a driver. Players particularly place importance on flight distance in shots with a middle iron and with a long iron. A spin rate of a golf ball in hitting with a middle iron is high. If a conventional golf ball is hit with a middle iron, an excessive lift force is generated. The lift force may cause rising of the golf ball during flight. The rising impairs flight performance. There is room for improvement also in flight performance in hitting with a middle iron.
An object of the present invention is to provide a golf ball having excellent flight performance. Another object of the present invention is to provide a golf ball excellent in both flight performance and feel at impact. Still another object of the present invention is to provide a golf ball excellent in both flight performance and feel at impact in hitting with a middle iron.